With a household of four preteen children, our poor old dishwasher often has to accommodate more dirty cups and glasses than plates. I’ve found that when you stack them on top of each other, they almost always need to be washed twice because the spray arms don’t reach everywhere (the cups, not the kids).
Although the bottom dish rack often has space left over, it’s designed for larger items such as bowls or plates, so I’ve figured out a way of making it accommodate cups and glasses. I unclipped the two plastic grids that usually hold down the glasses in the top rack and incorporated them into the bottom rack by means of cable ties, closing the large holes in order to put in more cups beside the plate pegs. I’ve not encountered any problems, and the cleaning and drying functions seem to be working normally.